Production of 2-methylhept-1-en-6-one

ABSTRACT

A process for the production of 2-methylhept-1-en-6-one by heating 2,2,6-trimethyl-3,4-dihydropyran in the presence of isobutene at a temperature of from 200* to 400* C.

United States Patent Mueller et al.

PRODUCTION OF Z-METHYLHEPT-l- EN-6-ONE Inventors: Herbert Mueller, Frankenthal; Hermann Overwien, Ludwigshafen, both of Germany Assignee: Badische Anilin- & Soda-Fabrik Aktiengesellschaft, Ludwigshafen/R- hine, Germany Filed: Jan. 18, 1971 Appl. No.: 107,589

US. Cl. ..260/593 R Int. Cl ..C07c 49/20 Field of Search ..260/593 R References Cited FOREIGN PATENTS OR APPLICATIONS 1,209,199 10/1970 Great Britain ..260/593 R Primary ExaminerLe0n Zitver Assistant Examiner-Leo B. DeCrescente Att0rney-J0hnston, Root, OKeeffe, Keil, Thompson & Shurtleff ABS IRACT A process for the production of 2-methylhept-l-en-6- one by heating 2,2,6-trimethyl-3,4-dihydropyran in the presence of isobutene at a temperature of from 200 to 400 C.

1 Claim, N0 Drawings PRODUCTION OF 2-METHYLHEPT-1-EN-6-ONE The present invention relates to a new process for the production of 2-methylheptl -en-6-one.

It is known from US. Pat. No. 2,628,252 that this compound can be prepared by adding on isobutene to butenone at superatmospheric pressure and elevated temperature. There is formed however a considerable amount of 2,2,6-trimethyl-3,4-dihydropyran, a compound which hitherto it has not been possible to exploit.

We have now found that 2-methylhept-1-en-6-one is obtained when 2,2,6-trimethyl-3,4-dihydropyran is heated to 200 to 400 C in the presence of isobutene.

It is a special advantage of this process that it is not necessary to use pure isobutene as a starting material but that fractions of C hydrocarbons which contain isobutene may also be used. Fractions having isobutene contents of at least 50 percent, particularly of from about 60 to 95 percent, are preferred.

2,2,6-trimethyl-3,4-dihydropyrane often occurs as a byproduct in the production of 2-methylhept-1-en-6- one, for example in the process of US. Pat. No. 2,628,252. It may however be obtained by other methods.

The molar ratio of isobutene to 2,2,6-trimethyl-3,4- dihydropyran may vary within wide limits, for example from 1:1 to 100:1, but molar ratios of from 10:1 to 50:1 are especially recommended.

The reaction is preferably carried out at from 250 to 350 C. Superatmospheric pressure is generally used, particularly from 50 to 500 atmospheres, preferably from 100 to 350 atmospheres.

The reaction may be carried out batchwise or continuously in the presence or absence of an inert solvent such as hexane, octane, benzene, toluene, diethyl ether, tetrahydrofuran, dioxan, methanol, ethanol or propanol.

The reaction mixture is worked up by conventional methods, for example by fractional distillation.

The 2-methylhept-l-en-6-one obtained according to the invention is a valuable intermediate for the production of odorants and compounds of the carotenoid series. For example the valuable perfume linalool is obtained in a simple manner from 2-methylhept-1-en-6- one by ethynylation followed by partial hydrogenation.

The following Example illustrates the invention.

EXAMPLE A mixture of 10 liters of isobutene moles) and 800 g of 2,2,6-trimethyl-3,4-dihydropyran (6.35 moles) is continuously fed per hour at 320 C and 240 atmospheres into an autoclave having an effective capacity of 6 liters. After conventional working up by distillation, 2-methylhept-l-en-6-one is obtained in a yield of 87 percent based on the amount of 2,2,6- trimethyl-3,4-dihydropyran reacted. Conversion is 62 percent; unreacted starting compound is returned to the reaction cycle.

We claim:

1. A process for the production of 2-methylhept-1- en-6-one which comprises contacting 2,2,6-trimethyl- 3,4-dihydropyran with isobutene in a molar ratio of from 1:1 to 1:100 at a temperature of from 200 to 400 C and a pressure of from 50 to 500 atmospheres.

" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3, ,3 Dated August 22, 1312 Inventor) Her-bent" Mueller, Hermann Overwien It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

over page ,insert [:30] Foreign Application Priority Data Jan; 27, 197 O Germany Signed and sealed this 19th day of March 197A.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

